In the early 1970s, Jambrek was close to the reformist wing of the Slovenian Communist Party, led by Stane Kavčič and Ernest Petrič. After the authoritarian turn in the Yugoslav Communist Party in 1972-73, which also affected Slovenia, Jambrek withdrew to purely academic work. He obtained professorship at the Faculty of Law and at the Faculty of Social Sciences of the University of Ljubljana. He studied conflict theory and published a sociological study on rituals and rebellions. Between 1973 and 1975, he taught at the University of Zambia in Lusaka. In 1975, he published a comparative study on the transformation of tribal societies into nation states. Between 1975 and 1982, he published several books analyzing the structure of political decisions in Yugoslav local government.

In 1989, he left the Communist Party and became a founding member of the Slovenian Democratic Union, one of the first democratic non-Communist parties organized during the Slovenian Spring, 1988-1990. After the victory of the anti-Communist DEMOS coalition in the first Slovenian free elections in spring 1990, he was appointed member of the Slovenian Constitutional Court. In the years 1990-1991, he became one of the foremost members of the Constitutional Committee that wrote the new Slovenian Constitution.

After characterizing the Slovenian Democratic Party as a party of "humiliated and insulted class, who never had privileges and who are frustrated because of that" (Slovene: "ponižanih in razžarjenih, nižjih slojev, ki niso nikoli imeli privilegijev in so zaradi tega frustrirani") in an interview published by Planet Siol.net,[4][5] he was accused of being an agent of the Yugoslav secret police,[6] and he is not involved in politics anymore.[7]